With the increasing concern of global climate changes, accurate solar radiation measuring instruments, such as radiometers, are becoming increasingly important. One problem currently faced when obtaining weather information is the buildup of dirt, debris, frost, rime ice, etc. that interferes with the instrument's sensing capabilities. Dirt and debris buildup often occurs on weather instruments regardless of their location. Rime often forms on the surface of weather instruments in extreme climates, such as in the Arctic; however, rime can be experienced in many other locations. Rime buildup can severely inhibit the measurement capabilities of many weather instruments, particularly radiometers. “Radiometer” as used in the present application is meant to include pyranometers and pyrgeometers as well as any other instrument capable of measuring solar radiation. Radiometers measure solar radiation flux from a field of view of approximately 180 degrees in a vertical plane and approximately 360° in a horizontal plane. A radiation transparent dome typically covers and protects the radiometer's sensor. Optically, the buildup of rime ice on the radiometer's dome can impede both shortwave and longwave radiation to the point where the readings of a rime covered radiometer cannot be distinguished from cloud coverage. Therefore, the information gathered by radiometers inhibited by rime or dirt typically results in inaccurate measurements.
There are several prior art approaches that attempt to address the problems associated with dirt and rime interfering with weather instruments, including radiometers. One approach has been to manually clean the instruments. An obvious problem with this approach is that the radiometer is required to be located at a manned weather station. This is often expensive and in some situations is not feasible. Furthermore, there is no way to keep the radiometer clean during periods between manual cleaning. Because of the severe limitations of this approach, manual cleaning is not an ideal solution.
Another prior art approach, particularly in colder environments where rime buildup is more of a concern than dirt, is the use of fans and/or heaters continuously blowing on the radiometer. It can easily be appreciated that this approach has the drawback of requiring substantial amounts of power. Generally, radiometers and other weather instruments positioned in extreme climates are designed to be self-powered, typically with solar powered batteries. As a result, the use of fans and heaters to keep rime from forming on the weather instrument consumes a substantial amount of power that may not be readily available. Consequently, this approach is generally only feasible where an AC-power source is available.
Therefore, there is a need in the art for a system capable of maintaining radiometers in an operational state by ensuring the sensor has a clean, substantially unobstructed view. The present invention overcomes this and other problems and an advance in the art is achieved.